Direct-viewing storage tube



Oct. 8, 1968 J. A. RADO DIRECT-VIEWING STORAGE TUBE Filed Dec. 9. 1966 VIEW AREA ROTATION INKENTOR. Jon/v Afmoo Gal 5. 6&2;

ERASE AREA \HEW AREA ERASE AREA Affame United States Patent 3,405,310 DIRECT-VIEWING STORAGE TUBE John A. Rado, Los Angeles, Calif., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed Dec. 9, 1966, Ser. No. 600,661 4 Claims. (Cl. 315-12) The present invention relates to a cathode ray tube and more particularly to that class of cathode ray tubes commonly called direct viewing storage tubes.

Cathode ray tubes are well-known in the art and generally the term cathode ray tube (CRT) refers to a class of tubes wherein a focused beam directly excites an output image. The basic elements are an electron gun, a phosphor screen and an envelope. The electron gun includes a thermionic source of electrons (a cathode) which is focused onto a phosphor screen. A deflection system is provided to deflect the electron beam in a desired pattern. The phosphor screen converts the electrical energy of the electrons beam into radiant energy, usually in the visible or near ultra-violet region of the spectrum. The envelope of the tube serves to provide a vacuum enclosure, a substate surface for the phosphor and a support and housing for the electron gun.

Direct view storage tube in addition to having the common elements of cathode ray tubes have a storage screen, a secondary electron collimating system and a reading gun. Normally, the storage grid is a dielectric material deposited on a fine metal mesh called the backing electrode, which is usually mounted between the collector electrode and the luminescent screen. The storage grid is charged to a uniform potential which is very near the viewing gun cathode potential. The writing gun scans the storage screen and creates a charge pattern on the surface of the storage grid by secondary emission from the dielectric material of the storage screen. As the dielectric material is an excellent insulator, the charge pattern does not leak away, but remains for a long period of time. The secondary electrons liberated from the storage surface are attracted to the collector electrode which is a very fine metal mesh pervious to electrons from the two types of guns. The reading gun does not scan the target system but instead the reading gun produces a wide angle beam of electrons which floods the entire target system and penetrates through the holes in the collector electrode and storage grid to bombard the luminescent viewing screen. The charge pattern written upon the storage screen controls the electrons from the viewing gun beam in a manner similar to the control of plate current by the signal applied to the control grid of a conventional triode vacuum tube. In this way the signals applied to the writing guns are converted to patterns on the storage screen and these produce corresponding patterns of luminescence on the viewing screen. In most display storage tubes, writing shifts the potential of the dielectric storage grid in a positive direction and manipulation of the backing electrode by voltage pulsing allows a negative charge to accumulate on the dielectric surface thereby erasing any stored information.

Most heretofore known cathode ray tubes, and also storage tubes, are stationarily mounted and deflection of the electron beam is accomplished in two planes by two pairs of deflector plates placed mutually at right angles. As the electron beam from a writing gun passes through one pair of deflector plates, the beam is deflected in a horizontal plane and as the electron beam passes through the other pair of deflector plates, the beam is deflected in a vertical plane. By controlling the amount of deflection in both the horizontal and vertical plane, a desired pattern can be depicted on the viewing screen.

The direct viewing storage tube of the present inven- 3,405,310 Patented Oct. 8, 1968 ice tion differs from heretofore known devices in that only a single pair of deflection plates are provided and the tube is rotatably mounted about a longitudinal axis. The electron beam is deflected in a horizontal plane only and vertical scan is accomplished by rotation of the storage tube. A flood gun is provided inside the envelope to provide an electronic cloud, which is modulated by a stored pattern which originated from a writing gun, to make a scene visible on the viewing screen. As the storage tube is rotatably mounted, novel means are provided for erasing the scene from the viewing screen.

.It is therefore a general object of the present invention.

to provide novel and improved means for storing and erasing a signal image on a storage screen.

Other objects and advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing wherein:

FIGURE 1 is a perspective view showing a direct viewin g storage tube of the present invention;

FIGURE 2 is a longitudinal sectional view of a rotatably mounted direct viewing storage tube;

FIGURE 3 is a sectional view taken on line 33 of FIGURE 2; and

FIGURE 4 is a sectional view similar to FIGURE 3 only showing another embodiment of the present invention.

Referring now to the drawing, there is shown in FIG- URES l and 2 a direct viewing storage tube having an evacuated envelope 11 which is comprised of an enlarged diameter portion 12 and two end portions 13 and 14 of reduced diameters. As the direct viewing storage tube of the present invention is to be rotated about its longitudinal axis, annular metallic bearing rings 15 and 16 are provided on the reduced end portions 13 and 14, respectively, to provide a bearing surface for rotation of the storage tube. A pair of slip rings 17 and 18 are provided on reduced end portion 13 and, likewise, a pair of slip rings 21 and 22 are provided on reduced end portion 14. It should be understood, of course, that a larger number of slip rings could be provided on the reduced end portions if the internal circuits of the direct viewing storage tube require a greater number of connections.

Referring particularly to FIGURES 2 and 3 of the drawing, reduced end portions 13 and 14 are rotatably mounted in bearings 23 and 24 and a gear 25 is provided so that the tube can be rotated. A stationarily mounted yoke 26 is provided around reduced end portion 14. An electron writing gun 27 is mounted within reduced end portion 14 and is capable of forming a well defined beam having high current density for providing high resolution and fast writing speed. The beam is deflected horizontally only by yoke 26 and vertical scan is produced by rotation of the entire viewing tube. The beam is directed onto a storage screen 28 which might be comprised of a dielectric material deposited on a fine metal mesh. A viewing screen 29, which might be of the luminescent type, is provided adjacent the envelope of the enlarged diameter portion 12. A reading gun 31 is positioned within enlarged diam eter portion 12 and produces a wide angle beam of electrons which floods the entire target assembly. Storage screen 28 is segmented, there being twelve segments shown in FIGURE 3 of the drawing, and an erasing commutator 32 is provided on each segment. By way of example, writing gun 27 and reading gun 31 might be of the type shown in U.S. Patent 3,160,773, which issued Dec. 8, 1964, to Eric Ziemer et al.

In operation, writing gun 27 produces an electron beam which is deflected horizontally onto storage screen 28 by yoke 26. During the writing, the entire storage tube is rotating about its longitudinal axis and thus vertical scan is achieved by this rotation of the storage tube. The writing gun 27 creates a charge pattern on storage screen 28 by secondary emission from the dielectric material. Reading gun 31 floods the storage screen 28 and penetrates through the charge pattern thereon to bombard the luminescent viewing screen 29 thereby providing a visible scene thereon. As best shown in FIGURE 3 of the drawing, storage screen 28 is segmented and an erasing commutator 32 is provided on each segment. As the storage tube is rotated, writing gun 27 Writes on storage screen 28 which can then be viewed in a view area. When, however, those segments of storage screen 28 are rotated to the erase area, an increased negative voltage is applied to those segments in the erase area whereby the writing on storage screen 28 is erased and is made ready to receive another scene upon being rotated to the writing area.

In FIGURE 4 of the drawing, there is shown another embodiment of a storage tube that is provided with a continuous cylindrical storage screen 33, which like storage s'creen 28 is comprised of dielectric material deposited on a fine metal mesh. The segment storage screen 28 which is shown in FIGURE 3 of the drawing results in a gap or discontinuity in the scene or picture being depicted, which gap or discontinuity may be objectional for some applications. The embodiment shown in FIGURE 4 of the drawing employs for erasing a segmented cathode 34, which by way of example, might have six segments 41 through 46. The three segments facing the view area, by way of example, might each have a voltage of volts applied thereto and the three segments facing the erase area might have a voltage of volts applied thereto. With the segments in the position as shown in FIGURE 4 of the drawing, segments 41, 42, and 43 would be at 10 volts and segments 44, 45, and 46 would be at 20 volts. After a rotation of the viewing tube in the amount of 60 degrees, segments 41, 42, and 46 would be at 10 volts and segments 43, 44, and 45 would be at 20 volts. An accelerator grid 47 is provided around the segmented cathode 34 to create a strong field to prevent any erase electrons from straying into the viewing area, which could reduce the allowable read-out time, or also could cause shading.

The operation of the embodiment of the storage tube shown in FIGURE 4 of the drawing is similar to the operation of the embodiment shown in FIGURE 3, except for the operation of the erasing structure. A writing gun 27 produces an electron beam which is deflected horizontally only and vertical scan is achieved by the rotation of the entire storage tube.

It can thus be seen that the present invention provides a direct viewing storage tube having improved means for storing and erasing a signal image on a storage screen.

' Obviously many modifications and variations of the present invention are possible in the light of theabove teachings. It is therefore to be understood, that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A direct viewing storage tube comprising an evacuated envelope including a central enlarged diameter portion and first and second reduced diameter portions connected concentrically with and extending outwardly from the ends of said enlarged diameter portion,

means for rotaing said evactuaed envelope about its longitudinal axis,

a target assembly within said enlarged diameter portion comprising a storage screen and a viewing screen,

a writing gun within said first reduced diameter portion for providing a pattern on said target assembly,

a yoke stationarily mounted around said first reduced diameter portion for deflecting horizontally electrons from said writing gun onto said storage screen,

a reading gun within said evacuated envelope for flooding said storage screen with electrons, and

means for erasing said pattern from said target assembly. 2. A direct viewing storage tube as set forth in claim 1 wherein said storage screen is comprised of annular segments spaced apart from one another and wherein,

said means for erasing said pattern from said target assembly includes a commutator on each said annular segment whereby a voltage source is selectively connectable to each said annular segment.

3. A direct viewing storage tube as set forth in claim 1 wherein said storage screen is comprised of a fine metal mesh cylinder having a dielectric material deposited thereon and wherein said reading gun includes a cathode having a plurality of annular segments and wherein said means for era-sing said pattern from said target assembly includes means for selectively regulating the voltage applied to each said segment of said cathode.

4. A direct viewing storage tube as set forth in claim 3 wherein an accelerator grid is positioned between said segmented cathode and said storage screen.

References Cited UNITED STATES PATENTS 3,3 19,105

5/1967 Koda et all. 313149 

1. A DIRECT VIEWING STORAGE TUBE COMPRISING: AN EVACUATED ENVELOPE INCLUDING A CENTRAL ENLARGED DIAMETER PORTION AND FIRST AND SECOND REDUCED DIAMETER PORTIONS CONNECTED CONCENTRICALLY WITH AND EXTENDING OUTWARDLY FROM THE ENDS OF SAID ENLARGED DIAMETER PORTION, MEANS FOR ROTATING SAID EVACTUAED ENVELOPE ABOUT ITS LONGITUDINAL AXIS, A TARGET ASSEMBLY WITHIN SAID ENLARGED DIAMETER PORTION COMPRISING A STORAGE SCREEN AND A VIEWING SCREEN, A WRITING GUN WITHIN SAID FIRST REDUCED DIAMETER PORTION FOR PROVIDING A PATTERN ON SAID TARGET ASSEMBLY, A YOKE STATIONARILY MOUNTED AROUND SAID FIRST REDUCED DIAMETER PORTION FOR DEFLECTING HORIZONTALLY ELECTRONS FROM SAID WRITING GUN ONTO SAID STORAGE SCREEN, A READING GUN WITHIN SAID EVACUATED ENVELOPE FOR FLOODING SAID STORAGE SCREEN WITH ELECTRONS, AND MEANS FOR ERASING SAID PATTERN FROM SAID TARGET ASSEMBLY. 